Try the free app Bitsboard.
Have a look at the resources on: https://www.speechandlanguagekids.com/free-materials/
Have a look at the resources on: https://chatterpack.net/blogs/blog/list-of-free-speech-language-communication-and-send-resources-for-schools-and-parent-carers
Colourful Semantics have a wealth of resources for free to support early language and sentence construction: https://integratedtreatmentservices.co.uk/our-approaches/speech-therapy-approaches/colourful-semantics-2/
The Communication Trust has many links to different resources for parents as well as schools (some free) as well as offering some free training which is very interesting: https://www.thecommunicationtrust.org.uk/