as long you are only forwarding Minecraft’s 25565 port to your server machine, it should be fine. Just make sure to keep Online mode on, use the whitelist, and get your plugins from trusted sources. Otherwise I wouldn’t worry too much.

I see others recommending VPN solutions like zerotier for your friends to connect to; I don’t personally feel like this is necessary, and (in my experience), making your friends do more technical setup than just connecting to the server is often a big turn-off.

Bonus: If you ever take a peek at your server logs while it’s running (and exposed to the Internet, if you avoid said VPN solutions), you might notice a lot of weird connections from IPs and usernames you don’t recognize. These are server scanners and threat scanners that look for vulnerable servers to connect to and exploit. This is normal and you’ll be fine as long as you keep that whitelist and stay up-to-date on developments in the server admin space.