Thanks. PKCE is not an alternative to code. PKCE is an addition to the code flow to prevent code replay and it is recommended by the OAuth 2.0 Security Guidelines (https://tools.ietf.org/html/draft-ietf-oauth-security-topics-13#section-3.1.1).
As I stated, use a public client (i.e. w/o a secret). That’s the same recommendation as for native apps (https://tools.ietf.org/html/bcp212). Clearly, the AS must take this into consideration when determining the level of trust it puts into the client‘s identity.