I encountered the same issue after importing my 2FAS entries into Proton Authenticator.
The TOTP codes are correct, but missing icons make the list less readable.
In my case, Proximus and Omada TP-Link both fall back to letter-based icons.
I have also submitted a separate request to add these two issuers to the automatic icon mapping.

Additional it should be possible to change the name of an entry, because some services are stored with an "official/legal" name different from the "public" one.

This is a super critical feature. They should've added it in the first place. Right now I can't pick service icons for each codes which is a massive pain

Even quite well known services like NPM, Nord VPN, Deutsche Telekom don't get an icon set automatically. It really would be a big usability boost to be able to have the right recognizable icons when scrolling through a long list.

This is super important once you scale to hundreds of codes like I have. Just a sea of letters. I think the best workaround would be to have a website field I can fill in, then have the app go out and fetch the favicon or logo.