> is there a web interface for the Debian BTS yet?
Only for consultation. Submitting should be done through a mail client (I would advise against that) or using the dedicated bugs reporting tool, reportbug: https://wiki.debian.org/reportbug
> they tend to be a nightmare to use if your address is accessed via a webmail interface, like mine
Here I use only self-hosted e-mail, so there might be many problems with the Debian BTS that I never experience but are affecting many people.
Maybe this could help, but it assumes that one is already familiar with what an SMTP server is (and we can’t expect that from most users): https://wiki.debian.org/reportbug#Using_a_custom_SMTP_server
CC: Hailey (npub1qru…shcs)