How to bond multi PPPoE connections?

I have a D-Link DIR 882A1 with OpenWRT 21.02.5, I can dial 4x PPPoE connections with MACVLAN from my ISP, but only 1 connection active and I don't want use load balance MWAN3 as it is not working well with me.

I am trying to bind these 4x PPPoE connections into one link to increase download and upload bandwidth, I did some search it looks NIC bonding or MLPPP may help. However, I can not find any technical document or examples to learn.

Please can somebody shield the light of WAN bonding or MLPPP? How to bond these 4x PPPoE connections into one single connection? Thanks!

Bonding has to be implemented at both ends.
So your 4xPPPoE connections would have to be bonding enabled by your ISP - this is usually very expensive if available at all.
Bonding is mostly used in point to point links like long range wireless or microwave, for example if you are connecting two buildings together.

Thank you! How to configure it at my end? I installed kmod-bonding, proto-bonding, luci-proto-bonding and ppp-multilink, but don't know how to use.

I think you misunderstand. There is no point configuring at your end unless your ISP configures at their end first.
Have you purchased a bonding system from your ISP? If not then it will not work.