ENS, the Ethereum Name Service, is the "namespace" for .eth
names.
Other projects like Unstoppable Domains (UD), can issue and sell NFTs. You are correct to be careful of the issues, which were also written about by the author of ethers.js:
I’ve always had serious reservations adding UD to ethers, they were
fully aware of my concerns and have since made the problem worse by
adding more TLDs.
https://blog.ricmoo.com/unstoppable-and-the-infinite-sadness-203f13e86488
For some background, the issue I was concerned with is that ENS had
released an awesome DNSSEC registrar on Ropsten for .xyz and would be
releasing a similar registrar for all supported TLDs. Nick gave a
great demo at DevCon 3 in 2017 and it was epic; this would allow
traditional web domains to interoperate seemlessly on the blockchain,
a clear win for the Web3 universe! (FYI: it has since been launched on
mainnet and supports over 1,300 DNS TLDs, such as .com and .org)
Once .crypto becomes a gTLD (through an ICANN auction), this would
cause a name collision, since if someone tries to resolve
ricmoo.crypto, should it resolve against the ENS registry (which
resolves against the DNS system) or the UD registry? They would almost
certainly disagree and it is likely that whoever buys the .crypto gTLD
is intending for it to work correctly within the blockchain ecosystem.
Since then, they have been expanding the collection of TLDs being
issued (e.g. .wallet and .nft) which exacerbates the problem,
especially since these names will very likely be highly sought after
by the well-funded.
This then becomes not just a nuisance, but a security concern. A
malicious actor could purchase an intentionally-conflicting name, in
hopes that some services rely on the service they registered on
allowing them to receive ether, tokens or NFT’s intended for someone
else.