Upgrading Drupal

TL;DR: Some "site building things" that are in Drupal 7 Features are not in the Drupal 7 site database, and therefore don't get migrated in a Drupal 7 to Drupal 8/9/10 upgrade.

Whenever updating modules on an existing Drupal 7 site, I got lots of these error messages

Undefined index: php in system_requirements() (line 471 of xxxx/modules/system/system.install)

The code at that place reads

After migrating to 10.2.1

The first page is OK, but user login gives the following error :
The website encountered an unexpected error. Try again later.

Dear all Drupalers - 

I have a d7 site, and the time has finally come for the dreaded upgrade to d10 (i have a dev site in d10.2.1).

scenario: i have a “program” page, that has the program description, and a list of news items related to that specific program.

the program is content type “programs” and has a tax tag from vocabulary “Programs”, the news items are content type “newsitems’ also have a tax tag from vocabulary “Programs"

Dear All,
I'm trying for weeks now to ugrade, but without any success on this particular site.

Getting this output:
Problem 1
    - zendframework/zend-feed[2.11.0, ..., 2.12.0] require php ^5.6 || ^7.0 -> your php version (8.1.27) does not satisfy that requirement.
    - laminas/laminas-feed[2.12.0, ..., 2.12.3] require php ^5.6 || ^7.0 -> your php version (8.1.27) does not satisfy that requirement.
    - symfony-cmf/routing[1.4.0, ..., 1.4.1] require php ^5.3.9|^7.0 -> your php version (8.1.27) does not satisfy that requirement.