I went the /e/os way and quickly turned back. Not to dismiss the effort of the maintainers, but it really felt like a frontend on lineage os meant to sell alternative cloud services. I did not find convincing arguments over a bare lineage os and the pretty much forced /e/ cloud was a total turn off.

I went the “real” security / privacy way and switched to grapheneos. Very happy overall, already went thought with 2 major os updates, no issues whatsoever. Only issue would be if you want Google pay (won’t work on graphene). You’d need a pixel phone if that’s in your budget. The pixel phones are great at photos, but pretty “meh” otherwise

I’ve not used it for quite a bit, but look at Thunderbird (a mozilla project iirc), it might do what you want as far as email is concerned. However do note that Microsoft is really closing things down in outlook/office these days, they really don’t like people using a “real” Linux (they want people to use windows with all their crap and start menu ads, and just have a small Linux VM they call the wsl )