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Clients treat these outputs as standard

Sending to new Segwit addresses was always standard. However, spending from them is non-standard. Older example: https://mempool.space/pl/address/bc1sw50qgdz25j

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But may be add some filters to a client

And then, when a new address type will be officially introduced, it will be harder, because old clients wouldn't allow sending to them. For example: if you have pre-Taproot client, it can still send coins into Taproot, as long as it has Segwit implementation. The same with recently added anchors: https://mempool.space/address/bc1pfeessrawgf

And also, there are reasonable limits, for example you cannot have a Segwit address with more than 40 bytes, so it is two times smaller than OP_RETURN limit (so, if anyone would want to spam, then that person would abuse OP_RETURN anyway).