You should also write like this,

<field name="x" attrs="{'readonly': [('participate_process', '=', False), '|', ('state', '=', 'fine'), ('state','!=', 'ok')]}" >

it will be converted to like this.

Where participate_process = False and 
(state = 'fine' or state != 'ok')


https://stackoverflow.com/questions/45506255/odoo-multiple-condition-in-domain-error/45518277

https://www.surekhatech.com/blog/working-with-domain-and-polish-notations-in-od-1