Devices like the later examples in this thread are worth looking at, to get the reliability and fun factor in:
EDIT: the first modern new-from-the-eShop mini-PCs with four ethernet ports and N95 CPUs (or better) start around 130 EUR/ USD (but ~180-250 EUR/ USD is more commonly found), so don't overpay for an 'old' device (but you can sometimes find those for really little money, as in under 50 EUR/ USD).
Most cgNAT ISPs at least offer IPv6 connectivity, which can be an alternative for incoming connections (not perfect, but good enough for my needs). Otherwise you'd need either a remote (v-)server under your control (to act as mediator) or something like tailscale. I'm also behind cgNAT (new fibre ISP, who simply came to late to get IPv4 addresses and has to make do with 32'768 IPv4 addresses for their 1.5 million customers…), works well enough for me (connect in via wireguard, problem solved).