Why can't they provide betas as regular downloads?
Maybe bacause this is not feasible?
Egosoft typically updates its betas roughly on a weekly basis. And you do
remember GOG takes pride
in manual validation of uploaded releases for "quality assurance", right? Even if we (or Egosoft) somehow manage to convince GOG not to turn down obvious betas for lots of bugs (seriously, go check their logs for the upcoming 3.0 release), by the time GOG publishes our oh-so-special Linux version it will be obsolete.
I doubt any beta-testing can realistically function with our setup. And it is entirely GOG's fault for not providing Linux any support at all.
Honestly GOG for Linux is a piece of store right now; and I can not see the situation to change "in a foreseeable future". :)