Upgrade OC 9.1.2 to 9.1.5: cURL error 51: SSL: certificate subject name 'my.domain.com' does not match target host name 'localhost'

Upgrade via OC Administration App does report
cURL error 51: SSL: certificate subject name 'my.domain.com' does not match target host name 'localhost'
(my.domain.com is a substitute)

Is there a solution? Or is the only option to do an manual upgrade?

This problem seems similar to

Manual upgrades are always the best options as the updater app is known to not work that reliable.

In your specific case there was a longer discussion in [1] which led to a possible fix in [2]. However as you're on an outdated version 9.1.2 you don't have this fix yet and now facing this issue.

[1]

[2]