After updating today no kernel was offered; I still have:
# rpm -qa kernel\*
Somehow I'm missing instructions to get that kernel...
please, re\-read the QSB, you missed \*\*security\-testing repository\*\* :
> These packages will migrate from the security-testing repository to the
> current (stable) repository over the next two weeks after being tested
> by the community.  Once available, the packages are to be installed
> via the Qubes Update Tool or its command-line equivalents. 
The QSB provides the links to the documentation which explains how to update from security\-testing, else wait \~2 weeks\.
The kernel update is only if you use \`kernel latest\` \(i\.e\. 5\.5 kernel\), but you use a 5\.4 kernel\. The xen and intel\-microcode update is for everyone\.
Same for your post about XScreenSaver : \*\*security\-testing repository\*\*\.
I did all theses update on my Qubes\-OS host, from now, no detected issue\.