I assume you were taken down by the same bug, in the older entware getdns/stubby that took down RT-AC86u and other HND based asus routers, including the RT-AX88U at first.@vesalius … RT-AX88U
I had similar issues when I initially tried stubby, but since then @Odkrys compiled the latest Stubby and GetDNS for HND routers RT-AC86U, RT-AX88U, GT-AC5300, statically linked to OpenSSL 1.1.1a which beyond fixing the show-stopping bugs provided performance improvements through TLS 1.3.
@Xentrk incorporated them into his distro and with some help and code cleanup from heavy hitters here all has worked well for those of with ASUS HND based routers since then. Give it another shot, should be a much much better experience now.