I only listen to podcasts so you got the big ones: playback speed and remembering position.

Do you intend to support podcasts and audiobooks? Specifically, remembering it stopped playing? If so I will totally drop Finamp for this

Agreed. You need to be willing to migrate to FOSS software or else “switching to Linux” will be a total failure.

I think the key is you need to find FOSS software that works for you before migrating your OS. Most FOSS software will run on windows and sometimes MAC.

1-2 and 3 will be hard. You can find many tools that do something similar but it won’t be perfect. There are a few different music managers, and for office libreoffice is the go to.

4. try digikam, it supports all OSes

5. googling “Fujitsu snap scanner Linux” yielded a few blog articles on the matter. Seems it should be supported.

From what I understand nexcloud isn’t a mail server, only a client. I’d need something that can act as an SMTP bridge to actually send emails.

Proxmox is meant to be an appliance. Meaning, you shouldn’t mess with the base OS .

If you want a desktop it might be better to make a dedicated VM in proxmox for it.