i have a problem with this configuration. Let me explain.
the configuration is: spf fiber from my provider and 3 BGP peers, 2 ipv4 and 1 ipv6. all the eternet port are configured as a pppoe server.
the connected cliente have some problem with some website and when i check for update in mikrotik antennas i have connection timed out. i can't ping from antenna download.mikrotik.com but from ccr works all. can be a MTU trouble. all ethernet port have 1500 as MTU and PPPoE client has 1480. in the mangle i don't have any roules but on PPPoE server profile Change MTU is setted as YES

I have 1480 MTU on every RB in my network and I don't have this issue, it isn't the cause of the problem
By the way if you want 1500 MTU set MRRU to 1504 in both PPPoE server and clients.

don't work, maybe is something in the mangle rule, i don't know where start. so the problem is not only in download.mikrotik, but also in some other website