APM MySQL Overview dashboard showing the following query
MySQL Databases\|<hostname>\|mydb\|......
instead of generic
MySQL Databases\|${Host_Name:regex}\|${Instance_Name:regex}\|.......
Checked this issue under other tenants, and it looks like it is also an issue there. It looks to be across all tenants. See same issue with many panels. It looks like an issue is with APM MySQL Overview dashboard only, Did check few other dashboards for APM MySQL and did not see the same issue.
DX SaaS
OI DEV team has made the necessary changes and provided the JSON dashboard (attached) which you can import into the tenant. The Out Of the Box dashboard will be updated in the upcoming DX SAAS release.