Hello.
You have to drop the indexes manually, connecting to mongo and running these commands:
db.rocketchat_nps_vote.dropIndexes()
db.users.dropIndexes()
db.rocketchat_room.dropIndexes()
db.rocketchat_message.dropIndexes()
db.rocketchat_integration_history.dropIndexes()
db.rocketchat_apps_logs.dropIndexes()
As discussed here: 4.4.0 Upgrade: Error creating index: users -> { bio: 1 } · Issue #24347 · RocketChat/Rocket.Chat · GitHub
This said, you will encouter other issues during this upgrade (trust me, you will!), like the "numRequestsAllowed’ error and if you are unlucky like me, you will alsso be stuck on this SSL error.
In my case, I reverted back to 3.18.7 cause it looks like it already fixed cve-2022-32211.
Another solution seems to upgrade first to 4.6 and then to 4.8, as stated here "numRequestsAllowed" property in rateLimiter not set after upgrade from 3.x to 4.x · Issue #26089 · RocketChat/Rocket.Chat · GitHub but I did not tried this yet.
Good luck!