When will we need to add more 0s or is it planned to keep it on a 2nd layer?

[AGD]

Just a few morning thoughts: 0.01 USD is already 21 Satoshis. Not too long before we need to add maybe two 0s. When the price for a Bitcoin is 1 Mio USD we still can keep the 1 Sat= 1 USD cent, but since fees are calculated in sat/b, fees will get absurdily high or am I wrong here? There will be a need for a hardfork to do that, right? Who will pay a value of 500$ for any Bitcoin transaction?

Lightning and other 2nd layer seem to solve this, but there will be a need to close a channel and public the transaction on the blockchain, which in the future may cost multiple times the value of the closed lightning channel.

If I am completely wrong here, please ignore.

Have a nice weekend!

[NotATether]

Basically if a fee is lower than a node's minimum relay fee (minrelaytxfee in the getmempoolinfo RPC call) then the node will not send the transaction to other nodes.

It's default value is a constant meaning it can be lowered in future versions if Core devs decide to do it, but everyone running older versions will still have 1 sat/vbyte as the minimum relay fee.

Alternatively some people can try to convince the older nodes to use the -minrelaytxfee argument or pass it in bitcoin.conf and give it a value lower than 0.0001 (sats/virtual KB, it's equivalent to 1 sat/vbyte).

[NeuroticFish]

When the price for a Bitcoin is 1 Mio USD we still can keep the 1 Sat= 1 USD cent, but since fees are calculated in sat/b, fees will get absurdily high or am I wrong here?

Your calculation sounds about right. But.. well, the miners have to earn something too. And it would be normal that at the point 1 BTC = $1M LN would be properly up & running & widely used. Yes, this means that although we'd love the high price, it may not come that early.
The point is that yes, at some point the fees will become prohibitive, but at that point one would no longer use on-chain transactions for withdrawing from faucets and buying a coffee.