CANON 90D vs CANON R10

I went from the M6ii which is a 90D close relative, to the R10.
If the R10 is "entry level" then the 90D should be considered, less than entry level when it comes to features and capabilities.
The only entry level aspect about the R10 is the battery door.
Another point in favor of the R10 is more lens options than 90D, considering you can use any EF, EF-S and R lenses, thus you can go super compact and discreet when need it. As a bonus you can use master filters, namely CPL or ND for all your EF, EF-S lenses via adapter.

Choosing the 90D would make sense if you can find it cheaper than the R10, you are not planning to buy more lenses and are ok with the 90D feature set, which honestly, is roughly 85% of what the R10 offers. In that regard, the 90D is like a 90D mark 2 would have been.

Fundamental differences among these two cameras revolve around EVF vs OVF, Size and Ergonomics. The 90D would have better handling simply because is bigger, but the R10 ergonomics are great for its size, much better than my M6ii.
The 90D higher pixel count sensor would outperform the R10 24Mp in terms of resolution only in very limited circumstances. For landscape it could be better *if/when* using sharp lenses with proper technique, on a tripod and electronic shutter mode.
Most of the time, I don't need super high rez, so the smaller file size of the R10 has been a blessing for me. If landscape is very important to you, the EOS R would be a better option but that is a FF camera.

Hope this help with your decision.