If you've lost your job as a result of COVID-19, be honest with the interviewer. As there are many people who have been or are being laid off as a result of the pandemic, and most employers are certainly aware of the situation. Or you may have other reasons, just tell the interviewer and try not to make up a story. You're also advised to explain that you have been actively searching for jobs and building skills while being unemployed. This shows the interviewer that you took initiative while being unemployed instead of doing nothing, simply wait for the pandemic period to end at someday. Wish you good luck!