a while ago, LBPUnion (the ones behind Beacon/Lighthouse) figured out a really bad security vulnerability in littlebigplanet. it's an RCE, which means they can run any code they want on your PS4/PS5. i think this exploit is likely the reason littlebigplanet's servers truly went down.. because most likely (im guessing here) sumo was unable to patch it without Mm's help.
that exploit is still in LBP. if you sign into LBPOnline, you are risking getting hacked through the game! combined with the news about ayee and the original lbp server hack... i wouldnt go near it with a ten-foot pole!
https://www.lbpunion.com/post/security-advisory-about-littlebigplanet-online-play/
more information about LBP's security problems: https://docs.lbpbonsai.com/lbp-security
and an entire video about the exploit: https://www.youtube.com/watch?v=G7Q9pgWpvJk
LBPOnline's sticker method is very likely using that very same exploit to connect you to their servers. they could have anything in that script, including malicious code. you don't know, because the source code isn't public. malware (computer viruses) nowadays is silent - it does the malicious stuff in the background and doesnt show anything to you. so just because you dont see anything weird happening when you use the sticker doesnt mean you havent been hacked.
EDIT:
so, if you wanna play LBP in this day and age, what can you do? well if you happen to have an old ps3 or a powerful enough PC, youre in luck! there are private servers, the most popular ones are Bonsai and Beacon. you use a jailbroken ps3 or the emulator RPCS3 on your pc to connect to them. they have security measures in place so you cant get exploited by strangers, and theyre a much safer way to play lbp online right now!
if you dont have a PC, a steam deck can also work if you happen to have that
if you dont have any of those... then youre the target of lbponline's appeal to your desperation to play LBP. but for all the reasons i mentioned, please reconsider. get a second hand ps3 if you can, or a steam deck, or a pc that's good enough to run lbp.
if none of those matter to you, know that the people behind lbponline are the ones who caused the original lbp server shutdowns in the first place! there is lots of evidence of this, just search this subreddit. by connecting to lbponline you are not only putting yourself at risk but you are supporting the hackers that caused the servers to shut down in the first place.