There has been a bit of confusion on how to file a TM30 now that they have stopped issuing TM6s (arrival/departure cards). Nothing has actually changed. Although there is a field to enter the TM6 code online it is not a mandatory field. You can file normally without one.
Also the new 90 day reporting system here [members only] does not require a TM6.
TLDR : Answer Summary
There has been confusion about filing the TM30 since the TM6 arrival/departure cards are no longer issued. However, filing remains straightforward as the TM6 code is not mandatory for the TM30 submission. Additionally, the new online 90-day reporting system does not require a TM6.