At my previous employer, a large network services provider, everyone got the same depth of support, even people that were on the free tier! Granted, the people paying us $ENTERPRISE usually got responses in minutes, whereas free users might be waiting around for a week on more difficult cases, but it was the same set of engineers working on each.
Free customers did report bugs, and we would replicate, triage, and fix them as usual. These tended to be more obscure bugs (more severe ones would usually surface in the paid queues first), but we didn't discard them immediately.
Whether we effectively ignored bugs depended more on the ability of the customer to provide an actionable report. Some users provide exactly what we need up front, but there is a lot of "it doesn't work!" white noise from users that aren't able to or aren't willing to put in the work to accurately describe their issue and/or action feedback from us. There's usually not a whole lot support can do in that scenario if we don't see any obvious issues, but we'd go a bit further to placate paying customers--I fondly remember joining a call between some very technically inept user and their ISP who was adamant that either we or the ISP were at fault, after we guided their network team through taking local packet captures showing unanswered SYNs past their network border.