Apache Web Server does not work

Dear community,

Apache server is not working for me on LEDE Reboot 17.01.4 r3560 running on Linksys WRT1200AC.

Apache cannot create threads, get wrong PIDs and replies on all GET requests with 500 Internal Error.

I tried first with the stock package: apache - 2.4.25-1, when compiled from https://github.com/openwrt/openwrt.git latest version 2.4.28-2 (incl. required dependent libraries) - same behavior.

I filed my findings in already opened bug report https://github.com/openwrt/packages/issues/4840.

Rest of the system works well, so it is not a hardware problem.

Sample error lines (more you can find in the referenced ticket):

[Sun Jan 21 22:08:29.002837 2018] [core:notice] [pid -5278272639347982336:tid 3069826204] AH00094: Command line: '/usr/sbin/httpd'
[Sun Jan 21 22:08:29.003540 2018] [proxy_hcheck:info] [pid 0:tid 3065494852] (70023)This function has not been implemented on this platform: AH03312: apr_thread_pool_create() with 16 threads failed

Does anybody experienced the same problem? What would be the approach to solve it?

Thank you and regards,