Cannot automatically upgrade from Tails < 4.15

Hi dear tails devs :)

I am in the shameful position to have a not up-to-date tails live usb. I currently am on 4.13 and cannot upgrade to the latest version because of something that seems closely related to #18127 (closed). Full details below.

The error

amnesia@amnesia:~$ tails-upgrade-frontend-wrapper 
localuser:tails-upgrade-frontend being added to access control list
Prototype mismatch: sub Tails::IUK::Frontend::assert ($;$) vs none at /usr/local/share/perl/5.28.1/Tails/IUK/Frontend.pm line 25.
Prototype mismatch: sub Tails::IUK::Frontend::__ ($) vs none at (eval 386) line 2.
Could not download 'https://tails.boum.org/tails-signing-minimal.key', request failed (SSL peer certificate or SSH remote key was not OK): server certificate verification failed. CAfile: /usr/local/etc/ssl/certs/tails.boum.org-CA.pem CRLfile: none
 at /usr/local/share/perl/5.28.1/Tails/IUK/Frontend.pm line 250.
localuser:tails-upgrade-frontend being removed from access control list

A detail: from the same shell, this command succeeds

$ curl -v --socks5 127.0.0.1:9050 https://tails.boum.org/tails-signing-minimal.key

Screenshots