I'm actually already avoiding this issue but for another reason: hackers will scan subdomains matching known products with known vulnerabilities, so hosting a Wordpress behind "wordpress.domain.tld" will get you way more ill-intentioned requests than "tbyehl.domain.tld".

Thus if I started hosting my Immich instance, I would probably put it behind "pxl.domain.tld" or something like that.

Not a garantee to pass the Google purity test, but, according to some reports, it would avoid raising some redflags.