All depend on the business profile and what they do to earn money.
There are a lot of solutions out there, but they have to adapt to the best one for their use case.

I wrote several guides about how small merchants and businesses can start accepting:

• Bitcoin for small merchants
• First steps to accept BTC as a merchant
• LNbits for merchants
• The Bank of LNbits
• Lightning wallets comparison
• Lightning Network submarine swaps
• Operating LN as a merchant

And additional guides:

• Lightning network si awesome
• Be your own bank - think like a bank
• What Bitcoin node software you could run?

More resources:

• Bitcoin Resources Page
• Lightning Resources Page