And the good news is, every Halo Insider is invited this time around. The next beta for the multiplayer component of the game is set to get underway later this month on the 24th of September, and every Halo Insider will be invited to take part.
You'll still need to be part of the Halo Insider program to get access, though. The good news is that at least right now, you can still sign up for the program, although 343 Industries has stated that only those who sign up before the 13th of September will be able to take part in the test. If you're interested, then head over to this link to get yourself registered.
As for what to expect in the beta, that's still a mystery, but the last test featured a limited selection of different maps and weapons for players to test with. There have been hints that PvP will be something that 343 want to test, however.
Halo Infinite will release on the 8th of December on PC and Xbox consoles.