Frank-Starr good luck. when this ever gets solved I will consider it un milagro.
I have Solus and I have Fedora. I have to keep them apart because I can't install them together. Solus first, Fedora second=fedora erases solus bootloader
fedora first, solus second=fedora erases solus bootloader.
Grub wins every battle but I'm not a grub pro.
With Fedora 38 (which Ultra should be updated but its only a week old) there is a mythical, magical EFI bootloader in the install that forsakes Grub...a new Fedora invention...so it will create a true /boot efi that can be shared with Solus...if Solus was there first. I have been too inept to use it since documentation gets so dodgy.
As fars the BRTFS I don't know.
As far as the shared /home I really doubt it but I will defer.
As long as you have the 1 MB bios boot img there, it won't share with Solus. You can install Solus ("alongside" but I usually create partitions) but as long as your sys thinks you are in BIOS/Legacy the solus bootloader won't have chance. Oh sure. sda2 will be the efi boot but its symbiotic (I think) with the sda1 boot.
I have read hours and hours about this and there are many success stories side by side but I could not make it happen.
If you take anything from my failure-ridden reply is I did not try Alongside of yet. The truth is you can successfully install them next to each other but only one will ever boot for me. Everything I read is about installing Fedora as UEFI, not legacy, first and go from there. I can't do that. I have a freaky "Legacy and UEFI" bios with doesn't really mean it with the UEFI. It's just kidding. you can boot legacy or legacy+uefi. Not uefi.
If you can make the boots work you will be in business. If I had a different MOBO this would be solved for me.
Another downside if the solus boot gets borked: programs like Refind and GrubRescue are basically useless for Solus because its boot isn't grub.
--Still I'd go forward with the install of solus 'alongside' and go from there. but you look like you have no ext/root space to spare (586MB?) and you have a ton of /home space you can shrink. I don't know how solus installer handles that. I'm sure it will see all that /home space and carve out a home there (maybe?)
Sorry for the mess hopefully you can find value somewhere here