I got curious about the domain handles used on Bluesky, so I analyzed 38.849 profiles.

2.795 users (7.2% of total) have custom domain handles.

The most frequently used TLDs for custom domains are:

com: 999
dev: 249
net: 152
me: 106
xyz: 93
io: 83
org: 67
social: 66
jp: 45
blue: 41