What is it ?

Terrestria is a mod adding a handful of new biomes featuring new custom trees and environments to navigate;
Many of the biomes take inspiration from ExtrabiomesXL in a similar way Traverse does.

What does it offer ?

New biomes alongside new wood types/trees (and one or two ground plants), which are more realistic/vanilla+ than fantastic.
Some biomes are really nice, some are emptier, it really depends on which one we are talking about;
The mod also features a small thing which is quarter logs (only for some of this mod's trees for now), which I think is a nice addition I hope to see added to vanilla Minecraft someday.

I will here list every biome and explain what I like (or dislike) about each of them :
Caldera
A nice mountain alternative with lakey valleys; A bit weird that in the most recent versions of the mod the water isn't turquoise like stated on the biome's wiki page, but I quite like the biome otherwise (one of the many biomes to feature the hemlock tree type)
Canyon
A mountaineous desert which looks different (and in my opinion better) than the various hilly dune-like biomes found within biomes o' plenty, I find it great to navigate without being too close to the badlands/mesa biomes in terms of global generation; this one is probably one of my favorite biomes added by the mod, and looks similar to the ice maze biome added by aquamirae (I wonder if there's some inspiration in one way or another between the two mods, but honestly it could be completely unrelated)
Cypress Forest
A somewhat dense biome with trees of gray wood, perfect for a hidden vacation resort; I like this biome, the trees generate often enough for it to feel similar to a small irregular maze of leaves, which is pretty satisfying to explore
Cypress Swamp
Although the out-of-water sections of the biome feel a bit boring to me, when half submerged it is a cool biome; probably my favorite biome from the mod, but it could be due to betweenlands/biome makeover nostalgia in all honesty
Dense Woodlands
A biome concept which is better done in plenty of other mods : having a full oak forest, like in the older versions of the game before birch was introduced
Dunes
A bit of a forgettable biome, fits as a desert variant to bring more verticallity in sandy biomes (there is already a biome in this mod doing exactly that but better from my perspective)
Hemlock Rainforest
Another Hemlock-adding biome, interesting both from the treetops and from the hillier grounds in terms of travel, I really recommend building something there if you explore it in survival (and the wiki does too apparently)
Japanese Maple Forest
Probably the most iconic biome from this mod, the japanese maple forest is pretty (prettier than biome o plenty's maple forest biome(s)); I think this biome could use some ground polishing on the ground though, it feels a bit too barren
Lush Desert
Saguaro cacti and thin Yucca trees in a regular desert, basically a more lively desert while still keeping the desert's identity. I wouldn't mind this biome ending up as a full replacement of the vanilla desert
Lush Redwood Forest
Prettier than the regular Redwood Forest proposed by the same mod, I don't have much to say about this specific biome
Outback
an Australia-sponsored biome with acacia bushes and yucca trees, it is not my favorite as I am usually not much of a fan of desert biomes (exceptions can be made)
It isn't the first time I've seen this biome concept within a mod, but it's still nice to see
Rainbow Rainforest
Remember when I stated there was that one cypress-based biome which was great in wetter sections but felt a bit too empty for my taste when above ground ? well this biome being more lush it features a lot more ground decorations and a vibe which makes me hesitate to switch my preferences, as it basically 'solves' my complaints about the other one
Redwood Forest
This one is pretty from above (and when exploring from the treetops) but a bit barren from the ground, it could use more ferns or rock formations to make the terrain more interesting (just like in real life)
Snowy Hemlock Forest
Another Hemlock-adding biome, interesting both from the treetops and from the hillier grounds in terms of travel, but with added snow
Volcanic Island
Just like how real-life islands are more often than created by volcanoes in the first place, this one is too, with the volcanic rock worldgen feature pulling lava from an underground lake; I think the volcanic rock blocks look really good, especially the dark green/black mossy ones, they can make for pretty buildings

Unlike Traverse, this mod doesn't have the "lack of ground decorations" issue I mentioned, and while the soil is still pretty uniform in each area, there's more custom shrubs and cacti participating in making the global terrain more lively.
However, the biome replacement system makes it so many of the naturally-generating biomes from this mod appear in smaller spaces (which is great if you want the biomes to be better ingrained within vanilla environments, but sucks a bit when trying to explore only one for longer; I would recommend selecting large biomes for the worldgen if you want to have fun within them more).
I would also like it more if the custom trees added by the mod had more utility outside of a decorative wood set (more unique things to do with the cypress/yucca trees for example ?), but for a vanilla-style biome mod which does not aim to add thousands of things, it adds things well and I am looking forward to the mod's future, hoping it will get even more interesting content updates.
I would like to mention that some biomes (mainly the oasis , but the sakura forest too) couldn't be force-located for some reason, it could be because they aren't implemented in 26.1.2 yet ? or maybe they are just very rare; Anyways I decided not to mention them in the biome list, you can check the mod's page for more information about them anyways.

In conclusion

I quite like this mod's looks and this mod's biome style, even if many are ideas I've witnessed before already (some better than here).
This mod has its own little wiki, having pages for each biomes listing the sources of inspirations and content/intent. There isn't much in terms of config option outside the ability to enable/disable each biome (which is already quite great to avoid overlapping content with other biome mods).
To me, this mod is even better than 1.12 Traverse, as not only does it features new biomes to integrate within your world, but many of them are actually interesting to traverse.

I always prefer a mod with fewer biomes over one with more but which aren't interesting/distinct enough to observe and walk through, this mod while being smaller than many is worth using.
Just like Traverse, this mod also has a reforged version which can be interesting for forge-based modpacks.