A few suggestions with points to consider for each. These can all run on mobile device with no separate device needed:

- Breez (self-custodial, point of sale interface, supports NFC, lightning and on chain although on chain with swap fees for on chain, no-KYC, no direct conversion to fiat)

- Phoenix (similar to Breez but no point of sale interface and no NFC)

- Wallet of Satoshi (custodial, point if sale interface, NFC support, lightning and onchain with swap fees for on chain, requires email to backup, no direct conversion to fiat)

- Strike (consumer focused, custodial w/ KYC, no dedicated point of sale interface but simple payment request screen, lightning and on chain, can choose to receive incoming Bitcoin payments directly as bitcoin or fiat and can convert between the two in app, withdraw/deposit direct to bank accounts)

- Cashapp (similar to Strike but can’t auto convert incoming payments to fiat but can sell bitcoin for fiat in the app, limits may be low for business use)

- Opennode (basically same as Strike with more tools and features designed for business vs. consumer focus with Strike, integrates with your website, auto withdrawal to bitcoin wallet or bank account depending on settings)